DescriptionDifferences in power and status are the basis for social relations and interactions within workgroups. While a small body of research has investigated the consequences of power and status in groups, there is a general emphasis in the extant literature to consider power and status independently, even though they can be causally related and mutually reinforcing. Therefore, the purpose of this dissertation is to explicate the opposing consequences of power and status in groups and also investigate the joint influence of power and status on psychological safety, collective efficacy, and workgroup effectiveness. Distinguishing power and status in groups, and also investigating the joint effects, are important advances to the existing group research, which has often confounded power and status. Additionally, clearly understanding the distinct group processes and outcomes that emerge from each group structure may mitigate any possible harmful effects that may occur in task-focused workgroups. Chapter 1 provides a brief overview of the central constructs and theory investigated in this dissertation. Chapter 2 provides conceptual and theoretical contexts for the exploration of the central constructs. Chapter 3 describes the hypothesized model. Whereas power differentiation is predicted to lead to higher psychological safety, collective efficacy, and group effectiveness, I predict that status differentiation will lead to lower levels of psychological safety, collective efficacy, and group effectiveness. Furthermore, I predict that power differentiation will have a more positive influence on group emergent states (psychological safety and collective efficacy) and effectiveness when status differentiation is lower within groups. Chapter 4 describes the research methods and results. Data were collected from two healthcare facilities, pilot study (18 workgroups) and main study (80 workgroups), to test the hypothesized model. As predicted, I found that power differentiation is negatively related to treatment errors. In addition, I found that status differentiation is negatively related to psychological safety and collective efficacy. Chapter 5 identifies implications for researchers and organizations and discusses additional points of interest for future research.